A semiconductor device using an organic semiconductor as an active layer is calling attention. The semiconductor device using the organic semiconductor is advantageous also for cost reduction because it is possible to form the active layer by applying the organic semiconductor material at a low temperature. Further, it is now possible to pattern and to form, not only the active layer, but also a gate insulating film layer, a source electrode, a drain electrode, and further a gate electrode, by applying a material that can be applied.
By forming the active layer and the like by a coating method, reduction of producing cost can be realized, and further it will become also possible to produce a semiconductor device including a flexible substrate having no heat resistance such as a plastic material.
In a coating method such as an inkjet method, material having a low viscosity is applied to a substrate and the like. In order to pattern a low-viscosity material by a coating method, a physical boundary is required to define a domain to be coated. Accordingly, a method of forming a bank around the domain to be coated is proposed in a coating method such as an inkjet method.
In Patent Document 1, there is described a method of forming an electrode by applying an electrode material to a domain enclosing a source electrode and a drain electrode, where the domain is defined by a bank on a substrate formed by nano-imprint (see Patent Document 1).
Further, in Patent Document 2, there is described a method of producing an organic semiconductor element by applying an electrode material and an organic semiconductor material to a domain enclosing a source electrode, a drain electrode and an active layer, where the domain is defined by a bank formed on a substrate by a photolithographic method (see Patent Document 2).
Patent Document 1: Japanese Patent Laid-Open Publication No. 2007-35981
Patent Document 2: Japanese Patent Laid-Open Publication No. 2006-245582